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Full text of "The manufacture and properties of iron and steel"

INTEODUCTION.                                              ffl
into the casting to supply the gap made by shrinkage. These /"sink-heads" or "risers" must be cut off by saws or otherwise, and it often happens that the surface so exposed shows a few holes. These holes do not indicate a bad casting, as the fault is purely local. On the other hand, it often happens that the casting is machined in one or more places, and this exposes minute blowholes. These usually are not serious, and, as a rule, the holes do no harm in themselves, as the strength of the casting is just the same as if an equal number of holes had been bored with a tool.
A casting of complicated shape is likely to be internally strained by the cooling of the mass. Certain parts will be in tension and .certain parts in compression. In simple shapes these conditions do .not exist to any extent, but in complicated forms it is well to anneal the whole casting. This process when properly conducted changes the crystalline structure and increases its ductility. The improvements invented in the last few years in the way of pyrometers allow this process to be carried out with scientific precision, instead of in the old haphazard method that often did as much harm as good.
Nothing is easier than to write the self-evident laws that should govern the inspection of steel, for the manufacturer should supply what is required and the inspector should receive nothing else. If the steel does not fulfil the specifications, it is the fault of the maker, and all the chances, and losses of error should have been taken into consideration in making the contract. Moreover, the inspector is only an agent, and he violates his trust in accepting anything that falls outside the limits which, either wisely or foolishly, have been set by his principal.
These facts are patent; but trouble does arise, and it will be to the advantage of all concerned if the points of difference are discussed. The main causes of disagreement are as follows:
(1)  Dishonesty of .the manufacturers.
(2)   Open disregard of specifications by the manufacturers.
(3)  Bad construction of the specifications.
../.'(4.) Conscientiousness and non-discretionary powers o_ the inspector.                   . The • dishonesty of the manufacturer is a sad fact which occa-